Magnetic structure for dynamoelectric machines



NOV. 1, 1938. T, G, YE 2,134,795

MAGNETIC STRUCTURE FOR DYNAMO-ELECTRIC MACHINES Filed July 14, 1956 INVENTOR The as G Myers [3% W ATTORN EY Patented Nov. 1, 1938 UNITED STATES PATENT OFFICE MAGNETIC STRUCTURE FOR DYNAMO- ELECTRIC MACHINES Application July 14,

6 Claims.

'This invention relates to magnetic structures for dynamo-electric machines, such as for in stance, the stators of induction motors.

The stator structures for such motors are usually made up of a series of slotted soft steel or iron punchings, which are held compactly together by appropriate fastening means, such as rivets. It is well understood that such laminations in a direction axial of the motor, serve to reduce eddy current losses which may become excessive unless this mode of construction is used.

The windings for the stator are accommodated in the slots. In order to improve the efliciency or performance of the motor, it has been proposed to provide slots that are closed or nearly closed. Under such circumstances, it is necessary to insert the windings or coils a few wires at a time through the slots. Such a procedure is expensive; and could not be effectively utilized for any except motors that operate under comparatively low electromotive forces, such as 400 volts. For higher electromotive forces, such as for 2200 volt operation, the insulation must be heavy and the coils form wound, precluding the possibility of this endwise insertion.

In order to obtain the advantages of closed slots, it has been proposed to use laminations having open slots into which the winding can be easily placed, and then to close the slots by a magnetic stick. Such a construction however has been found disadvantageous, for the eddy current losses in the sticks reduce the efliciency of the motor, and in fact may cause excessive heating of the sticks.

It is one of the objects of this invention to make it possible to utilize any form of winding in the stator slots, without the necessity of using loose wound coils, and yet obtain the advantages of closed slots without excessive eddy current losses.

It is another object of the invention to improve and simplify in general the magnetic structures for dyanmo-electric machinery.

It is still another object of the invention to provide magnetic top sticks for closing the slots, made in such fashion that the eddy-current loss is reduced to an immaterial amount.

In order to attain this object, the top sticks are made up of finely divided magnetic material, such as iron or soft steel, held together by a nonmetallic binder, such as a phenolic condensation product. The binder serves not only to hold the stick in shape, but to insulate the magnetic particles or groups of particles from each other. This effect can be produced readily by thoroughly 1936, Serial No. 90,556

mixing the binder and the powdered magnetic material prior to molding the sticks out of the composition. The solidifying of the sticks can be accomplished in the ordinary way, dependent upon the kind of binder used. When a phenolic condensation product is used, the intermingled mass is subjected to heat and pressure in a mold, in a manner utilized for molding Bakelite.

This invention possesses many other advantages, and has other objects which may be made more easily apparent from a consideration of one embodiment of the invention. For this purpose there is shown a form in the drawing accompanying and forming part of the present specification. This form will now be described in detail, illustrating the general principles of the invention; but it is to be understood that this detailed description is not to be taken in a limiting sense, since the scope of this invention is best defined by the appended claims.

Referring to the drawing:

Figure 1 is a fragmentary pictorial view of a top stick embodying the invention; and

Fig. 2 is a fragmentary sectional diagram of a magnetic structure embodying the invention. The top stick I can be made from a composition of from six to ten parts powdered iron or soft steel or other magnetic material, and about one part of resin or other non-metallic binder. These proportions are by weight. The ingredients in powder form can be first thoroughly mixed, and then molded by heat and pressure to the desired form.

The sticks l are shown in Fig. 2 as closing the slots 2 of the stator 3. The stator windings 4 are merely diagrammatically illustrated. The stator structure is shown as cooperating with a rotor structure 5 of the cast squirrel cage type.

The top sticks I may be provided with the sloping side wings 6 adapted to enter into the corresponding recesses I near the top of slots 2; thereby the sticks are locked against radial movement.

The sticks l are intended to be slipped or inserted in place from the end of stator magnet structure 3. This structure 3 may also be made up of a homogeneous mixture of a non-metallic binder and magnetic powdered material, such as iron or soft steel, in about the same proportions as used for the sticks I. This makes it possible to mold or form the stator magnet as a single piece, and with a consequent reduction in the eddy current loss; and yet obviate the necessity of punching out numerous sheet steel discs and the slots therein. The punched out, wasted portions in this former construction constitutes about one third of the steel blanks, corresponding to corners of the squares, and the winding slots.

What is claimed is:

1. A pre-formed top stick for closing the slot in a magnetic structure for dynamo-electric machines, made from a homogeneous mixture of divided particles of magnetic material and a nonmetallic binder, and adapted to entirely close the slot.

2. A magnetic structure for dynamo-electric machines, made from a mixture of divided particles of magnetic material and a non-metallic binder, in the proportion of about seven parts by weight of the magnetic material and one part by weight of the binder.

3. A top stick for closing the slot in a magnetic structure for dynamo-electric machines, made from a mixture of divided particles of magnetic material and a non-metallic binder, in the proportion of about seven parts by weight of the magnetic material and one part by weight of the binder.

4. A molded magnetic structure for dynamoelectric machines, made from a mixture of divided particles of magnetic materials, and a phenolic condensation product, in the proportion of about seven parts by weight of the magnetic material and one part by weight of the phenolic condensation product.

5. A pre-formed top stick for closing the slot in a magnetic structure for dynamo-electric machines, made from a homogeneous mixture of divided particles of magnetic material and a phenolic condensation product, and adapted to entirely close the slot.

6. A molded top stick for closing the slot in a magnetic structure for dynamo-electric machines, made from a mixture of divided particles of magnetic material and a phenolic condensation product, in the proportion of about seven parts by weight of the magnetic material and one part by weight of the phenolic condensation product.

THOMAS G. MYERS. 

